Corrected entry: When Rufus is jamming with Bill and Ted at the end of the movie, you will notice that when the camera switches shots and shows the close-up of Rufus's hands, his hands are black. Rufus is white throughout the movie.
Correction: I rewatched that scene, and Rufus's hands remain white.
Corrected entry: Toward the end, just before Bill and Ted's presentation in the auditorium, there is a shot of the stage, with the podium front, centre stage. After a cut to the teacher, it cuts back to the stage, and the podium has disappeared.
Correction: The camera cuts away for more than enough time for someone to have moved it offstage. After all, everyone thought that Bill and Ted were not going to show up, and that the presentations were over anyway.
Corrected entry: When the jewel is converted into the phone booth about 10 minutes in, there is a slight inconsistency between shots. The phone booth start to take shape from the crystal. The next shot with Rufus in his glasses, if you look closely, the phone booth is fully formed in the reflection, as you can see the word "Phone" at the top of the booth. In the next shot, the phone booth still isn't complete.
Correction: This was done on purpose. His glasses are reflecting a few seconds into the future. This happens one other time in the movie as well.
Corrected entry: As soon as Bill, Ted and Billy the Kid arrive in Greece, Billy is holding a modern day Nerf ball. Where did Bill and Ted get this ball? They didn't bring anything else with them when they first went back in time.
Correction: First of all, Billy the Kid didn't start playing with the ball until after Bill and Ted picked up Socrates and arrived in Medieval England, second, if you look closely at the backround when Bill and Ted are talking about princess babes, you can see Billy the Kid searching through a bag that Bill and Ted brought with them, and pulling out the Nerf ball.
Corrected entry: When Beethoven is playing the keyboards in the mall why would he be arrested if the sales associate prompted him to play and he was obviously drawing positive attention to the business?
Correction: The security guards could easily be arresting him for disturbance of the peace, or the salesperson in the store might be losing business because everyone is listening, no one is shopping. There are many possibilites.
Correction: The only time we actually hear the synthesizer is when Beethoven plays a few chords of what sounds like church music. When he's jamming in the mall later on, and then giving his concert during the report, all his music is covered by the soundtrack which is the guitar music we hear.
Corrected entry: In the scene when everyone is in the mall Beethoven is in the music store. The sales clerk turned on the drum machine on the keyboard and Beethoven reacted. This should not have happened since Beethoven was completely deaf - the movie had already established that Beethoven was deaf at that time. When Bill and Ted "landed" the telephone booth to get Beethoven he was playing the piano in front of a gathering of people. The phone booth made a loud noise that everyone listening to Beethoven play reacted to, however, Beethoven continued to play without a reaction - thereby exposing his deafness.
Correction: Beethoven could feel the vibrations of the drum machine through the keyboard; this is how he composed in his later years, by holding a stick between his teeth and placing it on the piano.
Corrected entry: In the scene where Ted falls down a spiral staircase, the stairs should spiral anti-clockwise, not clockwise. This is because in medieval times, the castle's defenders would have an easier time defending in this direction as almost all of them would have been right-handed.
Correction: This is true of most towers in castles, but some had staircases going the other way, so that if the castle was taken over, then they could have a slight advantage if they tried to recapture it.
Correction: Though it's a bit contrary to the form of time travel expressed in the movie, there's no reason meeting their future selves couldn't change said future, letting them do things a little different 'this time around'
Corrected entry: If Rufus is from the future where Wyld Stallyns music has changed why did he have to make sure Bill and Ted passed their report. If the world was like that then they obviously passed it.
Correction: But NOT until Rufus actually goes back to help them. It's what's called a "causality loop;" Rufus's future doesn't become firm until Rufus assists Bill and Ted.